High power amplifiers

Abstract

The specification describes an improved seed laser source for high power MOPA applications. Improvement is obtained by modulating the seed laser with a broadband noise function, for example, a Guassian noise function. A broadband noise function is one in which, in contrast to a sine wave function for example, has an RF spectrum with a bandwidth comparable in value to the mean frequency. Use of a broadband noise modulator allows effective tuning of the output of the modulated laser.

1 . Optical device comprising: 
 (a) a seed laser,    (b) a tunable phase modulator for modulating the seed laser, the phase modulator having: 
 (i) a phase modulation function that is a random noise source with an RF power spectrum in which the bandwidth is at least approximately equal to the mean frequency, and  
 (ii) a variable RF power input to generate an RF power spectrum with a variable linewidth.  
   
     
     
         2 . The device of  claim 1  wherein the random noise source has a Gaussian RF power spectrum.  
     
     
         3 . The device of  claim 1  wherein the RF power spectrum has a bandwidth at least 1.5 times the mean frequency.  
     
     
         4 . The device of  claim 1  wherein the RF power spectrum is produced using cascaded RF amplifiers.  
     
     
         5 . The device of  claim 5  wherein the cascaded RF amplifiers comprise at least two amplifier stages of at least one amplifier each, separated by a low pass filter.  
     
     
         6 . The device of  claim 1  wherein the wavelength of the seed laser is approximately 1550 nm.  
     
     
         7 . The device of  claim 1  wherein the wavelength of the seed laser is approximately 1080 nm.  
     
     
         8 . The device of  claim 4  further including a variable voltage source to vary the power to at least one of the amplifiers.  
     
     
         9 . The device of  claim 4  further including a variable attenuator to vary the signal to at least one of the amplifiers.  
     
     
         10 . The device of  claim 4  further including at least two filters with a switch for switching the signal between the filters.  
     
     
         11 . The device of  claim 1  wherein the laser is a pulsed laser.